Great Falls Exxon - PC20103028

Remediation Trailer behind TD Bank

Introduction

DEQ created this page to provide access to the technical reports and technical correspondence for the petroleum release at the former Exxon Service Station at 9901 Georgetown Pike in Great Falls, Virginia (the “site”). DEQ staff will typically post reports or technical correspondence on this webpage within 30 days of receipt, after staff has reviewed the information and confirmed that it is complete.

Links to Documents

Technical reports from the responsible person and DEQ regulatory letters can be found by clicking here.

A summary of DEQ's conceptual understanding of the release and groundwater at Great Falls is included as a PDF here.

Latest Site Status (2017)

The latest Corrective Action Plan (CAP) Implementation report was submitted on May 1, 2017 and is available on our Links to Documents page. The development of the former Exxon Service Station into a TD Bank has been completed. The on-site groundwater remediation was shut down while TD Bank was built and is due to start up again by the end of May. Groundwater samples taken during the system shut down show that methyl tert-butyl ether (MTBE) concentrations in the saprolite (weathered bedrock) aquifer at approximately 30 feet deep are very low. Concentrations in the bedrock aquifer (below the saprolite) are also low. In a localized area, however, the concentrations are elevated and have increased over the last six months of system shut down (but to levels well below concentrations at the start of the case). The groundwater remediation system will therefore need to be brought back on line to continue treatment of this “core” area. Downgradient of the “core” of the plume, concentrations in shallow and bedrock groundwater are low and generally trend lower.

Further investigation work carried out by the consultant for the owner of the new Exxon across Walker Road indicate that there are elevated MTBE concentrations in the saprolite aquifer beneath the new Exxon. This area of contamination is probably not from the closed former Exxon and may relate to a release dating from 2003 (when the station was branded as a Shell). While this area of contamination is small in extent and shows no sign of any significant movement downgradient, DEQ will task the responsible party with, over the next few months, further characterizing, and if necessary abating, that contamination.

The latest report is available on our Links to Documents page.

CAP Implementation Progress to April 2017

The corrective action started with a soil vapor extraction system and progressed to a combined soil vapor and groundwater extraction system. The current system involves groundwater extraction only as the soil vapor extraction system was switched off when contaminant recovery was complete and shallow groundwater contaminant concentrations were consistently low.

Groundwater recovery began from a single well (RW1) and between August 2014 and January 2015, the system recovered approximately 1.3 million gallons of water (an average groundwater recovery of 8 gallons per minute). This represents approximately 190 pounds of recovered MTBE. In January 2015 groundwater recovery began from a second recovery well (MW16D). Between January 2015 and March 2016, 4.4 million gallons of water (an average of about 7.5 gallons per minute) was recovered. This represented approximately 130 pounds of recovered MTBE. Between March 2016 and August 2016, about 1 million gallons of water, representing 15 pounds of MTBE, were recovered. By the time the groundwater remediation system was shut down to allow TD Bank to be built (after two years of operation), the MTBE recovery rates were significantly less(approximately 10%) of recovery rates in the first year of operation.


The chart above compares estimated mid-plume MTBE recovery between operation periods. This is typical of groundwater remediation systems and is consistent with overall reductions in available contaminant mass.

The groundwater treatment system appears to have lowered groundwater elevations beneath the former Exxon facility and a significant distance south and east The monitoring results indicate that the area of contamination, in both saprolite and bedrock groundwater has been captured or contained (i.e., no longer migrating with the groundwater away from the former station) to the west of Walker Road due to this change. The MTBE to the south appears to have been drawn or pulled back closer to the site boundaries. Additionally, the majority of the affected groundwater to the east of Walker Road has also been captured and reductions in concentrations across Walker Road appear to be occurring, but at a lower rate. As noted, recent work indicates that the MTBE east of Walker Road is probably not from the former Exxon. This area of contamination requires further characterization to establish whether natural degradation (indicated to be occurring from the ongoing monitoring) is sufficient to achieve remedial objectives or whether further remedial action is necessary.

This area of contamination requires further characterization to establish whether natural degradation (indicated to be occurring from the ongoing monitoring) is sufficient to achieve remedial objectives or whether further remedial action is necessary.

Overall, results continue to be consistent with the conceptual model for the site and suggest that the corrective action remains on target to achieve its objectives. DEQ anticipates that once the system is turned back on in the spring of 2017 it will continue to operate until the rate of MTBE recovery in the bedrock transition zone wells at the former Exxon drops to a lower percentage and the conditions east of Walker Road have been evaluated. Once consistently low rates of recovery are achieved, showing no significant recoverable contaminant mass exists, a shutdown of the system at the former Exxon may be appropriate. Post operational monitoring can then begin to evaluate whether there is any significant “rebound” in MTBE concentrations as groundwater elevations begin to rise.

A minimum of two years of post-operational monitoring will occur. Stable or reducing concentrations of MTBE that continue to meet the remedial objectives will need to be achieved before “case closure” will be considered.

Details of the vapor barrier and extraction system constructed beneath the TD Bank, required as part of the approved Corrective Action Plan, were included in Appendix C of the First Quarter 2017 Corrective Action Implementation Report.

Case History

In August of 2009, Exxon, through its consultant, Groundwater and Environmental Services, Inc. (GES), performed a site assessment at the property and discovered petroleum in the groundwater. They reported this finding, and DEQ assigned Pollution Complaint (PC) 2010-3028 to the case. During the latter part of 2009, Exxon performed initial abatement and site characterization activities at the site. As part of the site characterization, Exxon discontinued use of the on-site drinking water well and connected to municipal water. Exxon also identified and, where granted access, sampled drinking water wells within a quarter mile of the site.
Since 2009, groundwater monitoring has continued at the site and off-site potable wells have been sampled by DEQ’s petroleum program contractor, Stoner Culligan. There have been no confirmed detections of petroleum contaminants in samples taken from offsite potable wells.

In 2010, Exxon sold the property to Fairfax Petroleum Realty, LLC, which assumed liability for the cleanup. Fairfax Petroleum Realty hired Kleinfelder as its environmental consultant.  Kleinfelder has been conducting investigation activities since that time. Kleinfelder performed a Remedial Feasibility Study in early 2010, and a supplemental subsurface investigation in late 2011. In 2012, the service station was decommissioned and the underground storage tanks were removed.

On behalf of Fairfax Petroleum Realty, Kleinfelder submitted a draft initial CAP to DEQ in October 2013. DEQ met with the Great Falls Citizens Association (GFCA) Special Committee on Groundwater Contamination and subsequently requested that Kleinfelder make revisions to the draft. A revised initial CAP was submitted to DEQ on November 22, 2013. Public Notice was made in the Great Falls Connection newspaper on November 27, 2013. Comments were invited for a 30 day period from the initial public notice, or to December 27, 2013. DEQ held a public meeting to hear comments on the CAP on December 17, 2013, after the December GFCA meeting at the Grange, Great Falls. DEQ issued the CAP approval letter on January 27, 2014. The approval letter and a review of comments received and DEQ’s responses to those comments can be found on DEQ’s Links to Documents page.

In accordance with the CAP approved on January 27, 2014, Kleinfelder has been completing further investigations. They initiated a soil vapor extraction system in June 2014, completed a groundwater pump-and-treat evaluation in May and June 2014, and initiated a full time pump-and-treat system at the end of August 2014. A CAP Addendum detailing this work, and calculating remedial end points that will protect the beneficial uses of groundwater in the area, particularly the nearby private supply wells, was submitted to DEQ on October 2, 2014. The CAP Addendum was approved on March 2, 2015.

The soil vapor extraction system component of the corrective action operated from June 2014 to March 1, 2015. In the approximately eight months of operation Kleinfelder estimated the maximum recovery of volatile petroleum contaminants was just under 200 pounds. By September 2014, no measurable recovery of petroleum contaminants was occurring. MTBE concentrations in recovered vapor analyzed before system shut down contained 0.065 mg/m3, representing an approximate recovery rate <0.001/lb per day. Shut down was therefore considered appropriate. Since the vapor extraction system was shut down, remediation has been by groundwater, pump-and–treat, and natural degradation.

Contact

For further information, please email the DEQ Case manager, Alex Wardle, at alexander.wardle@deq.virginia.gov or write to:

Virginia Department of Environmental Quality, Northern Regional Office
13901 Crown Court, Woodbridge, VA 22193

Please include the pollution complaint number, PC2010-3028, in all correspondence. 


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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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